Materials with good stretchability and elasticity are used in a variety of applications for disposable and durable articles, such as in personal hygiene applications, roofing or flooring applications, packaging applications, etc. In hygiene applications including, incontinence pads, disposable diapers, training pants, clothing, undergarments, and sports apparel, comfort is a primary design consideration for a layer closely contacting with the body of the wearer.
Propylene-based elastomers, such as those commercially available under the trade name of Vistamaxx™ (ExxonMobil Chemical Company, Houston, Tex., USA) and VERSIFY™ (The Dow Chemical Company, Midland, Mich., USA) provide good stretchability and elasticity and therefore their use in the aforementioned applications has been considered. A foamed layer containing such propylene-based elastomers becomes more desirable because they further provide reduced tackiness and a light-weighing property in addition to stretchability and elasticity, which provides better comfort, for example, in hygiene applications, and reduces the cost of the raw material.
U.S. Patent Application Publication Nos. 2009/0105418 and 2013/102732 disclose a film composition comprising one or more propylene-based polymers and one or more hydrocarbon resins, and methods for making the same are provided. The propylene-based polymer may have (i) 60 wt % or more units derived from propylene; (ii) isotactically arranged propylene derived sequences; and (iii) a heat of fusion less than 65 J/g. The hydrocarbon resin may have a glass transition temperature greater than 20° C.
U.S. Patent Application Publication No. 2011/184127 discloses a film comprising one or more propylene-based polymers, one or more hydrocarbon resins, and one or more polyolefin additives provide enhanced mechanical and elastic properties compared to the neat propylene-based polymer. The propylene-based polymer may have (i) 60 wt % or more units derived from propylene; and (ii) crystallinity of from 0.25% to 40%, resulting from isotactically arranged propylene-derived sequences. The hydrocarbon resin may have a glass transition temperature greater than 20° C.
U.S. Patent Application Publication No. 2002/0151611 discloses a foam comprising a propylene-based copolymer material comprising at least 50 wt % of units derived from propylene, based upon the total propylene copolymer material, and units derived from ethylenically unsaturated comonomers and having a melt strength of at least 5 cN, and a melt drawability of at least 20 mm/s, process for making a foam using such a propylene copolymer material, process for making a foam in the form of thermoplastic foam bead using such a propylene copolymer material, and an expandable composition comprising such a propylene copolymer material.
U.S. Patent Application Publication No. 2009/0247656 discloses a closed cell foam material containing a propylene-based polymer comprising from 5% to 32% by weight alpha-olefin units. The propylene-based polymer has a heat of fusion, as determined by DSC, of less than 80 J/g. The material also contains 0.5 to 5 phr peroxide, 1.0 to 5.0 phr blowing agent, and 0.1 to 10 phr co-agent. The cells of closed cell foam material have a diameter in the range of 0.1 to 1.5 mm.
In particular, when making a foamed film or layer for the aforementioned applications, a cast film or layer may be preferable in terms of its good formability.
However, during a cast film processing, it is found the foamed material cannot be effectively drawn down to a desired thickness while maintaining the cell structures in good conditions in the foamed film or layer. It is believed that is because the melt strength of the propylene-based elastomer is low.
Therefore, there is a need to provide compositions and articles made therefrom that can provide a combination of stretchability, elasticity, softness, light-weighing properties, while maintaining good processability. There is also a need to methods of making such compositions and articles.